1. Field of the Invention
The present invention relates to a signal converter that outputs a measurement signal after converting a signal format of the measurement signal outputted by a measuring instrument into a predetermined signal format, a signal processor that is connectable with the signal converter and a signal conversion transmission system.
2. Description of Related Art
Traditionally, an apparatus (input tool) has been used for inputting a measurement signal outputted by a measuring instrument into an information processor such as a personal computer (see, for instance, Document 1: JP-A-60-177210).
The apparatus disclosed in Document 1 includes a signal transmission cable that connects a caliper gauge (measuring instrument) and a data processor to transmit the measurements by the measuring instrument to a data processor.
The measurement signal outputted by the measuring instrument is inputted/outputted via a unique serial port interface (I/F). Accordingly, when the measurement signal is inputted into, for instance, an information processor such as a personal computer (PC), the measurement signal has to be converted into a format suitable for the interface provided on the personal computer with the use of the above input tool.
Such an input tool converts the signal format of the measurement signal according to an HID (Human Interface Device Profile) keyboard protocol and transmits the converted measurement signal to a personal computer via a USB (Universal Serial Bus) connection. The input tool converts the measurement signal into a signal format specified for the HID keyboard protocol with an installed firmware for the HID keyboard protocol or with a hardware configuration according to the HID keyboard protocol. Then, the input tool outputs the measurement signal to a signal processor such as a personal computer via a USB connection interface (referred to as USB interface hereinafter).
On the other hand, many of recent personal computers have an HID driver that is capable of processing a signal of a format according to the HID keyboard protocol as a default in a device driver provided by an OS (Operating System). Accordingly, when the measurement signal converted according to the HID keyboard protocol is inputted to such a personal computer by the input tool connected via the USB interface, the inputted signal can be processed in the same manner as the data inputted via an HID keyboard connected through the USB interface.
However, some of application software (S/W) require input of a signal in a format according to, for instance, serial port protocol. Further, some of the application software require the use of different software interfaces (API: Application Program Interface) for the measurement signal. When the input tool only outputs a measurement signal in a format according to the HID keyboard protocol through the USB interface for such application software, the signal inputted to a personal computer may not accord with the API and thus may not be processable. Though an RS-232C connection input tool that is connectable via a serial port may be separately provided considering compatibility with the above API, separate provision of such input tools necessitates a production of a plurality of types of input tools, which increases the production cost.
Alternatively, a convertor chip for converting the USB interface into RS-232C interface may be provided. However, since it is necessary to separately provide such a convertor chip, the hardware configuration becomes complicated and the production cost increases.